via IMDB:

When his
lightning bolt is stolen, Zeus accuses Poseidon's son Percy Jackson and gives
fourteen days to Poseidon to return his lightning bolt; otherwise he would
initiate a war against his brother. Meanwhile the dyslexic and with ADHD
teenager Percy is visiting The Museum of Metropolitan of Art and is attacked by
a Fury disguised in his teacher. His crippled best friend Grover reveals that
Percy is a demigod and he is his protector and his teacher Mr. Brunner gives a
pen to him telling that it is a powerful weapon. They go to Percy's house and
together with his mother Sally, they drive to the Camp Half-Blood. However Sally
is attacked by a Minotaur and vanishes before Percy can help her. In the camp,
Percy befriends the gorgeous Annabeth; when they are attacked by Hades that
wants the lighting bolt for him, Percy discovers that his mother is in hell with
Hades. Percy decides to travel in a dangerous quest to retrieve the lightning
bolt and save his mother...